The present application relates generally to semiconductor devices, and more specifically to methods for manufacturing fin field effect transistors.
Fully-depleted devices such as fin field effect transistors (FinFETs) are candidates to enable scaling of next generation gate lengths to 14 nm and below. Fin field effect transistors (FinFETs) present a three-dimensional architecture where the transistor channel is raised above the surface of a semiconductor substrate, rather than locating the channel at or just below the surface. With a raised channel, the gate can be wrapped around the sides of the channel, which provides improved electrostatic control of the device.
The manufacture of FinFETs typically leverages a self-aligned process to produce extremely thin fins, e.g., 20 nm wide or less, on the surface of a substrate using selective-etching techniques. A gate structure is then deposited to contact multiple surfaces of each fin to form a multi-gate architecture over a channel region.
In a FinFET device, the raised fin architecture allows the channel to be extended vertically thereby increasing its cross-sectional area, which beneficially allows higher current flow through the channel without increasing the areal dimensions of the device. Another way to enable higher current without increasing the device footprint is to induce strain in the channel. As known to those skilled in the art, a compressive strain increases charge carrier mobility in a p-type metal oxide semiconductor field effect transistor (PMOS) channel, while a tensile strain increases charge carrier mobility in an n-type metal oxide semiconductor field effect transistor (NMOS).
During FinFET manufacture, an individual fin may be cut or severed to define distinct regions that may be used to form independent devices. Such a process typically involves etching unwanted portions of a fin to form a cut region, and backfilling the cut region with a dielectric material to isolate the remaining active regions of the fin on either side of the cut region. The resulting structure may be referred to as a single diffusion break (SDB), insomuch as the backfilled isolation dielectric defines a single region that prevents unwanted current flow between the two active fins that adjoin the SDB isolation structure. As will be appreciated, however, severing of the fin may have the undesired effect of relaxing the strain within the remaining portions of the fin.